Apparatus for operating electric discharge lamps and auxiliary lighting lamps

ABSTRACT

A ballast for mercury vapor lamps including an auxiliary incandescent lamp for providing illumination immediately after power to the ballast is momentarily interrupted during the hot restart condition of the mercury vapor lamp and also during the warm-up condition of the mercury vapor lamp. The ballast includes a high leakage reactance transformer having its secondary connected in circuit with the mercury vapor lamp. The auxiliary incandescent lamp is energized from a portion of the primary or from a separate winding inductively coupled with the primary. A photo-cell and switch arrangement, responsive to the light level of the electric discharge lamp, turns on the incandescent lamp during the hot restart condition of the mercury vapor lamp.

United States Patent Powell 51 July 25,1972

[54] APPARATUS FOR OPERATING ELECTRIC DISCHARGE LAMPS AND AUXILIARY LIGHTING LAMPS 3,209,202 /1965 Dunigan ..315/99 FOREIGN PATENTS OR APPLICATIONS 377,937 7/1964 Switzerland ..315/92 1,167,444 4/1964 Germany ..315/92 Primary Examiner-Roy Lake Assislant Examiner-Siegfried H. Grimm Attorney-Frank L. Neuhauser, Ralph E. Krisher, Jr., John M. Stoudt, Oscar B. Waddell, Joseph B. Forman and Radford M. Reams 57 ABSTRACT A ballast for mercury vapor lamps including an auxiliary incandescent lamp for providing illumination immediately after power to the ballast is momentarily interrupted during the hot restart condition of the mercury vapor lamp and also during the warm-up condition of the mercury vapor lamp. The ballast includes a high leakage reactance transformer having its secondary connected in circuit with the mercury vapor lamp. The auxiliary incandescent lamp is energized from a portion of the primary or from a separate winding inductively coupled with the primary. A photo-cell and switch arrangement, responsive to the light level of the electric discharge lamp, turns on the incandescent lamp during the hot restart condition of the mercury vapor lamp.

5 Claims, 5 Drawing Figures PATENTEnJuL 25 I972 SHEET 1 OF 2 ISIVEF-TOR, WALTER F POWELL AT TO RNEY PATENTEflJuLzs I972 SHEET 2 BF 2 IE- E INVENTOR.

ATTOR NEY APPARATUS FOR OPERATING ELECTRIC DISCHARGE LAMPS AND AUXILIARY LIGHTING LAMPS This application is a continuation of application Ser. No. 648,367, filed June 23, 1967, which application was co-pending herewith but is now abandoned.

BACKGROUND OF THE INVENTION This invention relates generally to apparatus for operating electric discharge devices such as mercury vapor lamps. More particularly, the invention relates to apparatus for operating electric discharge lamps and auxiliary lighting lamps in order to provide illumination during the time intervals when the electric discharge lamps are warming up or are out.

High pressure electric discharge devices, such as mercury vapor lamps, have been introduced for indoor lighting applications such as high bay factory installations as they have a greater light output and longer life than ordinary incandescent lamps. In addition, the color characteristics of these mercury vapor lamps have been vastly improved, and these lamps are now acceptable for indoor commercial and ofiice lighting applications. One problem associated with the use of mercury vapor lamps for indoor lighting applications, however, is the difficulty in restarting these lamps when they have been turned off. When power to a hot mercury lamp (or one operating for at least 1 minute) is interrupted and the lamp goes out, the lamp must cool down for approximately 2 minutes before an ordinary ballast circuit will be effective to restart the lamp. This cooling down interval may be called the hot restart condition of the lamp, and during this condition there is, of course, no light available from the mercury vapor lamp. This condition is generally not acceptable in the usual commercial installation. Accordingly, it is desirable that the ballast apparatus and its associated electric discharge lamps provide illumination during the time interval when the mercury vapor lamp is off and cooling down prior to being restarted.

Another problem associated with mercuryvapor lamps is that when initially turned on they operate at a low power level and hence provide a relatively low level of illumination. It would, therefore, also be desirable that the ballast apparatus and its associated electric discharge lamps provide a minimum illumination level during this warm up period.

It is, therefore, an object of this invention to provide a ballast apparatus for operating electric discharge lamps wherein illumination will be supplied during the time intervals when the electric discharge lamps are off and cooling down prior to being restarted.

It is another object of the present invention to provide a bal last apparatus for starting and operating electric discharge lamps wherein a minimum level of illumination is supplied while the electric discharge lamp is operating at reduced power during warm up.

It is a still further object of the present invention to provide a lighting system for electric discharge lamps wherein illumination is provided during the warm up and the hot restart conditions of the electric discharge lamps.

SUMMARY OF THE INVENTION In accordance with the invention, in one form thereof, a high leakage reactance transformer starts and operates a mercury vapor lamp connected in an operating circuit and an auxiliary lighting source in the form of an incandescent lamp. The incandescent lamp is connected in an auxiliary lighting circuit with a portion of the primary winding of the transformer, and is thereby constantly energized while the primary winding of the transformer is energized, wherein the incandescent lamp provides illumination during the hot restart and warm up conditions of the mercury vapor lamp.

In another embodiment of the invention, in one form thereof, a high leakage reactance transformer has an auxiliary winding inductively coupled with the primary winding, and the incandescent lamp is connected in an auxiliary lighting circuit with the auxiliary winding for energization at a reduced level below the rating of the incandescent lamp. In another aspect of the invention, a light responsive or variable resistance means, disposed to receive light energy from the mercury vapor lamp, is connected in circuit across the auxiliary lighting circuit wherein a low impedance path is provided in parallel circuit with the incandescent lamp when the mercury vapor lamp is on and a high impedance path is provided when the mercury vapor lamp is off. In yet another aspect of the present invention, a normally open switch means is connected in circuit with the light responsive resistance means, together with means for closing the switch means to turn on the incandescent lamp only when current in the operating circuit is interrupted, as when the mercury vapor lamp is out.

The subject matter which I regard as my invention is set forth in the appended claims. The invention itself, however, together with further objects and advantages thereof may be best understood by referring to the following description taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic circuit diagram of the lighting system in which one form of the present invention is embodied;

FIG. 2 is a schematic circuit diagram of a lighting system in which another form of the present invention is embodied;

FIG. 3 is a cross sectional view of a core and coil assembly utilized in the system illustrated in FIG. 2;

FIG. 4 is a schematic circuit diagram of a modified lighting system similar to that shown in FIG. 2; and

FIG. 5 is a schematic circuit diagram of another modified form of the invention similar to that shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, and specifically to FIG. 1 thereof, I have shown a schematic circuit diagram of one form of lighting system 10 in accordance with my invention. The lighting system 10 includes a ballast apparatus in the form of a high leakage reactance transformer 12, input leads l4 and 16 for connecting the transformer 12 to a source of alternating current (not illustrated), a power factor correction capacitor 18, and two pairs of output leads 20,22 and 24, 26. In addition, the lighting system 10 includes an incandescent lamp 28 and a mercury vapor lamp 30 mounted in side-by-side relationship in a lighting fixture 31. As will be seen in FIG, 1, the lighting fixture 31 includes a housing 33 for mounting on a panel 35, with the housing 33 having an internally mounted reflector 37 in which the mercury vapor lamp 30 and the incandescent lamp 28 are mounted.

The input leads l4 and 16 are connected to the primary winding 32 of the transformer 12, and in accordance with the usual practice, the transformer 12 has a core 34 and one or more magnetic shunts 36 for providing a predetermined amount of leakage reactance in order to limit the amount of current supplied to the mercury vapor lamp 30. The transformer I2 also includes a secondary winding 38 inductively coupled with the primary winding 32 in order to step up the voltage from the source.

While in the transformer 12 in FIG. 1, the primary winding 32 and a secondary winding 38 are shown in an autotransformer wound relationship, it will be understood that a transformer having a separate or isolated secondary winding may be utilized if desired. In either case, the mercury vapor lamp 30 is connected in an operating circuit with the secondary winding 38 by output leads 20 and 22 and output terminals 41 and 43. Also in the embodiment of FIG. I, the incandescent lamp 28 is connected in an auxiliary lighting circuit with a por tion 32A of the primary winding 32 by output leads 24 and 26 and output terminals 27 and 29. A terminal board 39 may be mounted on the fixture housing 33 to facilitate the making of connections to the lamps 28 and 30.

In operation, the mercury vapor lamp 30 is started by applying the open circuit voltage from the transformer secondary winding 38 across the lamp 30. Immediately upon starting, the lamp 30 will operate at approximately one-third power as it is warming up. This warm up condition lasts up to 1 minute, during which time the light output of the lamp is relatively low. After being started, the lamp 30 will remain in operation, being supplied with operating potential or voltage in the operating circuit. When the mercury vapor lamp 30 is extinguished, however, as when the power in the operating circuit is momentarily interrupted, it cannot be restarted for a time interval which may range from i to 5 minutes. While the mercury vapor lamp 30 is in the so-called hot restart condition and in the warm up condition, in accordance with my invention illumination is provided by the incandescent lamp 28 which in this embodiment is continuously energized so long as the primary winding 32 is energized. Thus, after a momentary power interruption the mercury vapor lamp 30 will remain out until it cools down sufficiently to be restarted, while the incandescent lamp 28 will come back on as soon as the primary winding 32 is re-energized and will thereby provide illumination.

As is well known, the operating life of a mercury vapor lamp will range from 6,000 to 20,000 hours while the operating life of an incandescent lamp is usually much shorter. Accordingly, in order to provide the incandescent lamp 28 with an operating life commensurate with the mercury vapor lamp 30, the incandescent lamp 28 is operated below its rating. In the exemplification, a 40 volt, 40 watt rated incandescent lamp is supplied with an operating voltage of approximately 30 volts in the auxiliary lighting circuit from the portion 32A of the primary winding 32 to which leads 24 and 26 are connected. In this manner, I have determined that the operating life of the exemplified incandescent lamp 28 should be as long as the operating life of the exemplified mercury vapor lamp 30. In the embodiment, the mercury vapor lamp is a,l volt, 250 watt lamp having the commercial designation H250-J 5.

In accordance with another embodiment of the present invention, I have provided the lighting system 100 illustrated in FIG. 2. In this lighting system 100, a high leakage reactance transformer 40, generally similar to that shown in FIG. I, is connected by input leads 48 and 50 to a source of operating potential such as 120 volt, alternating current supply. The transformer 40 includes a primary winding 42 and a secondary winding 44 connected in autotransformer relationship, and the magnetic shunts 45. A power factor correction capacitor 46 is connected in an output lead 51, and a mercury vapor lamp 67 is connected in an operating circuit with the output lead 51 and a second output lead 68. In this embodiment of my invention, an isolated, auxiliary winding 52 is mounted on the core 53 of the transformer 40, with the auxiliary winding 52 being inductively coupled with the primary winding 42. This auxiliary winding 52, together with output leads 54 and 56 connected thereto provide an auxiliary circuit for connection to an incandescent lamp 58.

Since it is desirable for reasons of economy to utilize essentially the same core design as used in the transformer 12 of FIG. 1, while also providing the isolated auxiliary winding 52, I have reduced the usual conductor size of the coil used as the primary winding 42 of the transformer 40. It will be seen in FIG. 3 that the auxiliary 52 is wound over the primary winding 42 and insulated therefrom by an insulator 55, in the same core window 57 of the transformer core 53. The primary winding 42 in the exemplification will have 374 turns of 0.0380 of an inch conductor wire, and the auxiliary winding 52 will have l5 turns of 0.0380 of an inch conductor wire. The core 53 is a well-known type having a T section and two modified L sections.

The incandescent lamp 58 shown in the exemplification of FIG. 2 may be a 6 volt, 23.5 watt lamp. Therefore, when the power supplied to the primary winding 42 is [20 volts, for example, approximately 4.8 volts will be applied to the incandescent lamp 58. The lamp 58 will thereby have an operating life approximately equal to the projected operating life of the mercury vapor lamp 67 since it is being operated below its ratmg.

The mercury vapor lamp 67 and the incandescent lamp 58 of the exemplification of FIG. 2 are mounted in juxtaposed relation in the reflector 63 of a lighting fixture 65. If power to the operating circuit is momentarily interrupted, the mercury vapor lamp 67 will be turned off and will remain 05 during its hot restart condition while the incandescent lamp 58 will come back on to provide illumination while the mercury vapor lamp 67 is cooling down. The incandescent lamp 58 will thereby provide illumination, albeit at a reduced level, until such time as the mercury vapor lamp 67 can be restarted.

In FIG. 4, I have shown a modification of the lighting system of FIG. 2 and have therefore used like numbers to designate like parts. In the lighting system of FIG. 4, the incandescent lamp 58 will operate at a reduced level when the mercury vapor lamp 67 is on, as the current supplied thereto in the aux iliary lighting circuit is less at this time.

In order to vary the current supplied to the incandescent lamp 58, and hence to vary the light output from this lamp, a resistor 70 is connected in the auxiliary lighting circuit in series circuit relationship with the lamp 58. A light responsive or variable resistance means in the form of a photoresistive light cell 72 is connected by the leads 74 and 76 across the auxiliary lighting circuit output leads 54 and 56 in parallel circuit relationship with the incandescent lamp 58. The light cell 72 is of the type that decreases in resistance when it receives light energy, and increases in resistance as the light energy decreases. Thus, the light cell 72 will be disposed in a position in the reflector 63 adjacent the mercury vapor lamp 67 in order to receive light energy from the mercury vapor lamp (the light cell 72 is shown schematically in FIG. 4). When the mercury vapor lamp 67 is on, the light cell 72 will thereby represent a low resistance path in shunt with the incandescent lamp 58, thereby reducing the current available to the lamp 58, and the light output of the lamp 58 will be low. Conversely, when no light is available from the mercury vapor lamp 67, the light cell 72 will offer almost infinite impedance inthe shunt path across the incandescent lamp 58, and full power will be applied to the incandescent lamp from the auxiliary winding 52. In this manner, the operating life of the incandescent lamp 58 will be increased as it will usually be operating at a very low level, and will receive full power from the auxiliary winding only when the mercury vapor lamp 67 is out. In addition, since full power is applied to the incandescent lamp 58 only when the mercury vapor lamp 67 is out, the voltage supplied by winding 52 can be higher than the lamp voltage, thereby obtaining greater illumination from lamp 58, without appreciably shortening the operating life of the lamp 58 Referring now to FIG. 5, another modification of the basic lighting system of FIG. 2 is shown, again with like parts denoted by like reference numerals. In this embodiment of the invention the lighting system includes the high leakage reactance transformer 40 having a primary winding 42, a secondary winding 44 and an auxiliary winding 52. The operating circuit for the mercury vapor lamp 67 includes the secondary winding 44 and the output leads 51 and 68, with a power factor correction capacitor 46 connected in output lead 51.

The auxiliary lighting circuit shown in FIG. 5 includes an auxiliary winding 52 and its output leads 54 and 56 for connection to the incandescent lamp 58. The light cell 72 is connected across the leads 59 and 56 and serially connected with a relay coil 78, with the combination being in shunt with winding 52. In this embodiment of the invention, a switch means in the form of a reed switch 73 is connected in series circuit relationship with the incandescent lamp 58 by lead 75 for turning the lamp 58 on only when the mercury vapor lamp 67 is turned off. In order to control the operation of the reed or magnetically actuated switch 73, switch actuation means in the form of the reed switch or relay coil 78 is connected in series circuit with the light cell 72 by leads 54 and 59.

In accordance with the operation of the lighting system 100 shown in FIG. 5, the mercury vapor lamp 67 will initially be started by the open circuit voltage across the secondary winding 44 of the high leakage reactance transformer 40. While the mercury vapor lamp 67 is on, the light cell 72 will receive light energy therefrom, the resistance of the light cell 72 will be low and the reed switch coil 78 will be energized sufficiently to maintain the contacts of the switch 73 in the open position. At this time, due to the open circuit condition in a series loop in cluding the auxiliary winding 52, switch 73, and incandescent lamp 58, the incandescent lamp 58 will be unexcited or in an off condition. When the light cell 72 no longer receives light energy from the mercury vapor lamp 67, however, the resistance of the light cell will increase, and the reed switch coil 78 will not be energized, The contacts in the reed switch 73 will therefore close, and current will'flow in the aforementioned series loop. The incandescent lamp 58 will thereby be turned on and will provide illumination during the time interval in which the mercury vapor lamp 67 is out. In this manner, the incandescent lamp 58 is only turned on when the mercury vapor lamp 67 is turned ofi, and thus the effective operating life of the incandescent lamp will be appreciably increased. In this arrangement also, the lamp 58 can be operated at an overvoltage to provide high illumination without appreciably shortening its life, as the lamp 58 will only be on for short intervals.

While in the exemplifications of FIGS. 2-5 described above, I have shown various specific features of the invention, it will be appreciated that this invention is basicallyconcerned with the use of an auxiliary lighting means in conjunction with a high pressure electric discharge device of the type that cannot be readily started when in a hot condition. The invention provides an inexpensive yet effective means of using mercury vapor lamps in commercial installations where outages of such lamps are undesirable, Although in the specific exemplificaappended claims to cover all such equivalent variations that come within the true spirit and scope of my invention.

l. A ballast apparatus for supplying operating potential from a source of electric energy to at least one electric discharge lamp of the type that requires a waiting period to be restarted when turned off while in a hot condition, and to an auxiliary lighting source, said apparatus comprising: a high tions of FIGS. 4 and 5 I have shown light cells for controlling the output of the incandescent lamp in response to the light output of the mercury vapor lamp, it will be understood that other arrangements such as a current sensing device may be provided to sense the condition of the mercury vapor lamp and to operate the incandescent lamp. Furthermore, it will be appreciated that the ballast circuits of these exemplifications are not limited to the use of high leakage reactance transformers, but that other current limiting means may be utilized to provide a lighting system that comes within the contemplation of my invention.

From the foregoing discussion of the advantages of the invention and the above description of the various exemplifications thereof, it is to be understood that many other modifications may be made by those skilled in the art, without actually departing from the invention. It is, therefore, intended in the leakage reactance transformer having a primary winding for connection to the source of electric energy, a secondary winding inductively coupled with said primary winding and current limiting means limiting the current in the said secondary winding; input means for connecting the at least one electric discharge lamp in an electric circuit with said secondary winding; and an auxiliary lighting circuit for connecting the auxiliary lighting source to receive reduced voltage electric energy through said primary winding independent of said current limiting means; whereby if the at least one electric discharge lamp is turned off in a hot condition, the auxiliary lighting source will provide illumination at least until the at least one electric discharge lamp is restarted.

2. The ballast apparatus of claim 1 wherein said auxiliary lighting circuit is effective to connect the auxiliary lighting source in electric circuit with a portion of said primary winding.

3. The ballast apparatus of claim 1 wherein said auxiliary lighting circuit includes an auxiliary winding closely coupled with said main winding.

4. The ballast apparatus of claim 1 including light responsive variable resistance means connected in said auxiliary lighting circuit for varying the current supplied to the auxiliary lighting source, said variable resistance means being disposed in light receiving relationship with the at least one electric discharge lamp whereby the supply of current from the source of electric energy to the auxiliary lighting source will vary with the amount of light energy received by said variable resistance means from the at least one electric discharge lamp.

5. The ballast apparatus of claim 4 including switch means connected in series circuit relationship with the auxiliary lighting source, switch actuation means operatively connected with said switch means, said switch actuation means being connected in series circuit relationships with said variable resistance means whereby said switch means will operate to turn on the auxiliary lighting source only when said variable resistance means senses that the at least one electric discharge lamp is oil. 

1. A ballast apparatus for supplying operating potential from a source of electric energy to at least one electric discharge lamp of the type that requires a waiting period to be restarted when turned off while in a hot condition, and to an auxiliary lighting source, said apparatus comprising: a high leakage reactance transformer having a primary winding for connection to the source of electric energy, a secondary winding inductively coupled with said primary winding and current limiting means limiting the current in the said secondary winding; input means for connecting the at least one electric discharge lamp in an electric circuit with said secondary winding; and an auxiliary lighting circuit for connecting the auxiliary lighting source to receive reduced voltage electric energy through said primary winding independent of said current limiting means; whereby if the at least one electric discharge lamp is turned off in a hot condition, the auxiliary lighting source will provide illumination at least until the at least one electric discharge lamp is restarted.
 2. The ballast apparatus of claim 1 wherein said auxiliary lighting circuit is effective to connect the auxiliary lighting source in electric circuit with a portion of said primary winding.
 3. The ballast apparatus of claim 1 wherein said auxiliary lighting circuit includes an auxiliary winding closely coupled with said main winding.
 4. The ballast apparatus of claim 1 including light responsive variable resistance means connected in said auxiliary lighting circuit for varying the current supplied to the auxiliary lighting source, said variable resistance means being disposed in light receiving relationship with the at least one electric discharge lamp whereby the supply of current from the source of electric energy to the auxiliary lighting source will vary with the amount of light energy received by said variable resistance means from the at least one electric discharge lamp.
 5. The ballast apparatus of claim 4 including switch means connected in series circuit relationship with the auxiliary lighting source, switch actuation means operatively connected with said switch means, said switch actuation means being connected in series circuit relationships with said variable resistance means whereby said switch means will operate to turn on the auxiliary lighting source only when said variable resistance means senses that the at least one electric discharge lamp is off. 